Using field jesses while hunting your hawk is advisable because they...

Using field jesses while hunting your hawk is advisable primarily because they serve multiple important functions that contribute to the safety and control of the bird. One key role of field jesses is to prevent the bird from getting entangled in trees, which can be a significant hazard when hunting in wooded areas. This helps ensure the bird's safety while navigating through dense foliage.

In addition, field jesses are crucial for keeping your bird from leaving the fist when startled. This is particularly important in a hunting scenario when sudden movements or unexpected noises can cause the bird to take off, potentially leading to a loss of the bird. By using jesses, falconers can maintain better control over their hawks, enhancing the overall safety of both the bird and the handler during the hunt.

The other options regarding disease prevention do not directly relate to the use of field jesses during hunting. Thus, combining the protective functions of jesses supports the conclusion that they are vital tools for controlling the hawk while also minimizing the risks associated with hunting.